1. Field of the Invention
The invention relates in general to a method for packet transmission scheduling and to a packet transmission scheduling system and specifically to a UMTS packet transmission scheduling method and to a System having UMTS packet transmission scheduling functionality.
2. Description of the Related Art
The invention addresses the problem of efficient scheduling of data flows, especially in Universal Mobile Telecommunication Systems (UMTS) for a transfer of data between a local base transceiver station (BTS) and e.g. a mobile station also termed user equipment (UE), i.e. for the UMTS Downlink Shared Channel (DSCH) between the base transceiver station and the mobile station. In the base transceiver station the radio access network has a complete or perfect knowledge of how much, when, and to whom packet transmissions are made or will have to be made within a certain interval of time. Hence, a central controlled unit may be and is used for the downlink data transmission.
However, in packet switching networks the task of multiplexing essentially reduces to the task of ordering packets and to then send them serially over a shared link. This process of serialization is referred to as scheduling. The benefit of packet switching is based on the multiplexing gain, where some data flows benefit from unused resources from other temporarily inactive data flows. The disadvantage of this service compared to a circuit switched service is a lack of predictability in such systems. Significantly, predictability of system behavior is one important measure of quality. Some services as e.g. internet communication or facsimile transmission services need stronger Quality of Service or “QoS” guarantees than others as for example pure speech data transmission. Quality of service (QoS) scheduling tries to balance the amount and timing of the received service for each flow according to the respective data flow requirements.